The long range objectives of this project are to determine the exact metabolic site or sites of action of important cardioactive drugs, ions and hormones in myocardial tissue. The relationships between these cardioactive substances, myocardial contractility and levels of important metabolic intermediates will be correlated. Substances such as digitalis, beta adrenergic agents, glucagon, calcium ion, lidocaine, beta adrenergic blocking agents, phosphodiesterase inhibitors and insulin will be studied. Initially the relationship between these agents and hormone second messengers cyclic AMP and cyclic GMP will be determined in perfused frog ventricles and isolated rabbit atria. In addition, studies will be conducted to determine the turnover rate and whether specific pools of these cyclic nucleotides exist within the myocardial cell. Cyclic AMP and cyclic GMP specific activity will be determined in tissue prelabeled with adenosine or guanosine using high pressure ion exchange chromatography. A new high pressure liquid chromatographic method will be developed to rapidly measure over 60 important nucleotides, sugar phosphates and other phosphorous containing intermediates of metabolism, rapidly and with subpicomole sensitivity. A high sensitivity gas chromatographic phosphorus detector will be interfaced with the liquid chromatograph. A complete analysis should take less than two hours. Once this instrumental method of analysis is on stream, the inotropic influence of drugs, ions and hormones will be related to these metabolic parameters. In addition, new and unknown hormone mediators which may be unnoticed by other analytical methods could be discovered through this analytical approach to analysis of metabolism.